I'm neutral in this debate, but I've discussed this with Ray in the past.
The issue is this, Ray is of the opinion that the tan color appears too uniform and too light in color to be rusted metal.
I used to argue with him, taking your point of view.
Ray found a shipyard worker many years ago that claimed there was at one point tan coloured non skid that was tested on forrestal and enterprise, I think.
Unless proven otherwise, it's impossible to say one way or the other if tan non skid was ever used.
The points I see that support this theory are,
Only two carriers have photos that look this way.
Other photos of rusty decks look different in color and uniformity.
I highly doubt a carrier would be on sea trials with an unpainted deck.
There is more than one type of nonskid and carriers used to use different ones for the landing area vs the rest of the deck.
I've personnaly seen many tests and experiments of different colours of anti fouling paint that aren't well documented.
So basically, I feel its possible that tan non skid existed for a short period.
One other thing, when you say the landing area is painted, I hope you mean the markings only, because if the whole area were painted grey, it would lose its flight certification.
I hope that helps a bit to understand why Ray is so convinced of the tan nonskid, and I hope Ray doesn't mind me summarizing for him.